On an irregular site that he disparaged as “almost non-existent” in 1968, Mies van der Rohe designed his last building, One IBM Plaza. Last month, the 52-story tower located in downtown Chicago and completed in 1972 was added to the National Register of Historic Places. The designation is notable in that it comes 12 years before the usual 50-year trigger for National Register significance to be considered.

The Illinois Historic Preservation Agency announced the listing of the building on March 26, citing “its exceptional importance in the area of architecture as one of Chicago’s premier examples of the modern movement style of architecture and the work of a nationally significant architect.” In 2008, the IBM building was designated a Chicago Landmark. The most recent honor comes with no obligations to its owners to maintain the building as is, although major alterations would probably prompt its removal from the National Register. Three other buildings in Chicago by the architect have already been designated, including the twin towers on Lake Shore Drive, listed in 1980, and Crown Hall, landmarked in 2001, at the Illinois Institute of Technology.

Final plans for the IBM building were completed by Mies, then 83, and his office in July 1969; he died on August 19. The second-tallest structure by the architect and the third-tallest building in Chicago at the time of its completion, the IBM building incorporates many of Mies’ signature moves, while also featuring advanced technological refinements initiated by the client, IBM, then at the height of its power as a computer technology innovator. The architect worked with firm partner Bruno Conterato on the project, and Conterato saw it through to completion.

Mies placed the building on the north end of the site, orienting it toward Bertrand Goldberg’s rippling Marina City towers to the west and the Sun Times building (now demolished) to the east. The curtain wall is composed of steel-framed anodized-bronze tinted aluminum and bronze glass in a grid of vertical rectangles so regular that they do not vary even when spaces within are double-height. Square structural columns are clearly expressed, stressing verticality, though recessed throughout the curtain wall and exposed at the base.

The material finishes in the lobby are typically Miesian in quality. Polished pink, black, and tan granite floors extend from inside to a loggia plaza created by the inset lobby. Walls are made of grain-cut and matched travertine slabs to enhance the impression of a single continuous piece of marble. The ceiling of pink glass mosaic is 26 feet above, lending the space a monumental quality that the architect believed essential to complementing the building’s overall scale.

No less impressive is the engineering for the building, developed in association with C. F. Murphy in order to accommodate the technological needs of IBM’s enormous computers, including temperature and humidity control. Other innovations range from radiant cooling and computer- controlled elevators to a plastic thermal barrier for preventing heat loss through the glass curtain wall. Soon after completion, the building was awarded the Federal Energy Commission’s first Midwest Excellence Award for Energy Conservation.

The building represented a culminating moment in IBM’s rise and it was the largest building the corporation had yet built. Today, however, IBM is no longer a presence in the building, now more commonly known by its address, 330 North Wabash Avenue. In 2006, its current owners, the Lightstone Group, briefly flirted with turning part of it into condominiums, and instead of The Sun Times, its neighbor is now Trump International Hotel and Tower. While it is rarely considered in the same breath as Mies monuments such as Crown Hall, the Seagram Building, or the Farnsworth House, the IBM building remains a singular structure emblematic of a singular talent at a singular time—well worth listing by the National Register.